This invention relates to a method and apparatus for determining the quantity of material in a tank, such as a satellite fuel tank, by radiation detecting means.
It is known to measure the quantities of the liquid within a tank, by using radiation sources positioned at the tank and a detector positioned for receiving radiation from the sources which has passed through the contents of the tank and is thereby attenuated. The greater the amount of the contents in the tank, the larger the attenuation will be of the detected radiation.
In most devices presently in use, radiation sources all of the same energy output and half-life are utilized. If a high-energy radiation source is used, the percentage attenuation of the energy output decreases greatly when the fuel level of the tank is low, leading to less accurate measurement of the quantity of fuel. Alternatively, if a low-energy radiation source is used, the attenuation of the radiation therefrom is relatively large when the fuel level of the tank is high, again leading to inaccuracy in the measurement of the contents. Devices in the prior art which utilize radiation sources of different energy outputs and half-lives require separate detectors for each radiation source.
If is an object of this invention to provide a new and improved method and apparatus for gauging the contents of a tank utilizing radiation sources of different energy outputs and half-lives for improved accuracy.
It is another object of this invention to provide such a method and apparatus utilizing a single radiation detector for detecting radiation from sources of different energy outputs and half-lives.
It is yet another object of this invention to provide such a method and apparatus wherein erroneous background radiation is eliminated from the measurement of the contents of the tank.
It is a further object of this invention to provide such a method and apparatus wherein calibration data are generated and stored which relate to detected radiation as a function of the quantity of material in the tank.
Other objects, advantages, features and results will more fully appear in the course of the following description.